Police officers carry a lot of equipment on their belts - handcuffs, CS spray, a baton, radio, a mobile phone, perhaps. In North Wales, some officers are finding room for another gizmo: a personal digital assistant (PDA).

North Wales police is one of the first forces in the UK to issue officers on the beat with PDAs permanently connected to the force's main IT systems.

Other forces will watch closely to see how the technology copes with front-line policing. In general, police IT systems, like those in the rest of the criminal justice system, are in a mess.

Over the years, each force has built up an individual mix of legacy systems, few of which communicate. The result? Officers spend large amounts of their day re-keying data between different systems.

This does not sit well with government targets for more officers on the beat. Mobile computing should help by allowing officers to sort out their paperwork when they stop and search a suspect, or make an arrest, rather than later. Mobiles also open the way for applications such as "video witness" - showing electronic mugshots of suspects to crime victims in their homes.

North Wales, which covers a huge area including large cities as well as Snowdonia National Park, has a special need for mobile computing. As part of an IT strategy that involves replacing about 30 legacy systems, it has issued PDAs to about 50 officers. The plan is to issue 1,000 over the next three years to its 1,500 officers. Others will have tablet PCs. The device will depend on the job, says Mike Hughes, project manager.

"A town-centre community officer who spends a lot of time on foot may be best served by a PDA, whereas a firearms team in a vehicle would be best served by data tablets."

Both types of terminal communicate with head office via general packet radio service (GPRS), an always-on service operating across GSM mobile telephone systems. Like other police forces, North Wales is introducing the national Airwave digital radio service - one of whose selling points was the ability to carry data as well as voice messages.

The problem is that Airwave doesn't have as much bandwidth for data. Hughes sees no problem with a "mixed economy" of complementary mobile data communications: Airwave for messages, GPRS for integration with headquarters IT systems.

Inevitably, there are other technical and practical problems to solve, quite apart from finding room on police officers' belts. And as always, the big issues are what consultants call cultural - how will police officers on the front line actually use the devices?

One worry is that officers will be physically overloaded. Another burden could be on the way - new fixed penalties for loutish behaviour may require officers to add portable printers to their kit. Computers also need look ing after, and may themselves be targets for criminals.

North Wales has found that the way to get constables to take care of their computers is to issue them as personal kit, rather than leaving them on a rack for general use. So far, the main effect of the mobile technology has been to reduce the amount of time officers spend in stations.

"You're in and out of the station quicker when you're dealing with prisoners," says Inspector Rob Kirman of North Wales police. The real gains will come later, if and when criminal justice systems are integrated. An officer will fill in an electronic form with the suspect's essential details at the time of arrest.

Assuming that information is correct, the information would not have to be re-keyed during the entire process. In theory, the data would be re-used by the courts, the prison service and probation.

Already, the system is saving an officer 15 minutes to an hour on every shift, Kirman claims. "It's about reducing crime, reducing fear of crime by putting people out on the streets."